//
//  Protected.swift
//  Extensions
//
//  Created by yiwanjun on 2022/3/11.
//

import Foundation

private protocol Lock {
    func lock()
    func unlock()
}

extension Lock {
    /// Executes a closure returning a value while acquiring the lock.
    ///
    /// - Parameter closure: The closure to run.
    ///
    /// - Returns:           The value the closure generated.
    func around<T>(_ closure: () -> T) -> T {
        lock(); defer { unlock() }
        return closure()
    }
    
    /// Execute a closure while acquiring the lock.
    ///
    /// - Parameter closure: The closure to run.
    func around(_ closure: () -> Void) {
        lock(); defer { unlock() }
        closure()
    }
}

/// An `os_unfair_lock` wrapper.
public final class UnfairLock: Lock {
    private let unfairLock: os_unfair_lock_t
    
    init() {
        unfairLock = .allocate(capacity: 1)
        unfairLock.initialize(to: os_unfair_lock())
    }
    
    deinit {
        unfairLock.deinitialize(count: 1)
        unfairLock.deallocate()
    }
    
    func lock() {
        os_unfair_lock_lock(unfairLock)
    }
    
    func unlock() {
        os_unfair_lock_unlock(unfairLock)
    }
}

/// 通过注解方式把一个属性包装成线程安全的属性 A thread-safe wrapper around a value.
@propertyWrapper
@dynamicMemberLookup
public class Protected<T> {
    
    private let lock = UnfairLock()
    private var value: T
    
    init(_ value: T) {
        self.value = value
    }
    
    /// The contained value. Unsafe for anything more than direct read or write.
    public var wrappedValue: T {
        get { lock.around { value } }
        set { lock.around { value = newValue } }
    }
    
    public var projectedValue: Protected<T> { self }
    
    public  init(wrappedValue: T) {
        value = wrappedValue
    }
    
    /// Synchronously read or transform the contained value.
    ///
    /// - Parameter closure: The closure to execute.
    ///
    /// - Returns:           The return value of the closure passed.
    public func read<U>(_ closure: (T) -> U) -> U {
        lock.around { closure(self.value) }
    }
    
    /// Synchronously modify the protected value.
    ///
    /// - Parameter closure: The closure to execute.
    ///
    /// - Returns:           The modified value.
    @discardableResult
    public func write<U>(_ closure: (inout T) -> U) -> U {
        lock.around { closure(&self.value) }
    }
    
    public subscript<Property>(dynamicMember keyPath: WritableKeyPath<T, Property>) -> Property {
        get { lock.around { value[keyPath: keyPath] } }
        set { lock.around { value[keyPath: keyPath] = newValue } }
    }
}
// 集合类型的线程安全方法
// 使用方式：定义变量时加上 @Protected ， 使用时带上$符号
// 例如：
// 定义 @Protected var atomicArray = [Int]()
// 使用 self.$atomicArray.append(1)
public extension Protected where T: RangeReplaceableCollection {
    /// Adds a new element to the end of this protected collection.
    ///
    /// - Parameter newElement: The `Element` to append.
    func append(_ newElement: T.Element) {
        write { (ward: inout T) in
            ward.append(newElement)
        }
    }
    
    /// Adds the elements of a sequence to the end of this protected collection.
    ///
    /// - Parameter newElements: The `Sequence` to append.
    func append<S: Sequence>(contentsOf newElements: S) where S.Element == T.Element {
        write { (ward: inout T) in
            ward.append(contentsOf: newElements)
        }
    }
    
    /// Add the elements of a collection to the end of the protected collection.
    ///
    /// - Parameter newElements: The `Collection` to append.
    func append<C: Collection>(contentsOf newElements: C) where C.Element == T.Element {
        write { (ward: inout T) in
            ward.append(contentsOf: newElements)
        }
    }
}
// Data 的线程安全方法
// 使用方式：定义变量时加上 @Protected ， 使用时带上$符号
// 例如：
// 定义 @Protected var atomicData: Data = Data()
// 使用 self.$atomicData.append(newData)
public extension Protected where T == Data? {
    /// Adds the contents of a `Data` value to the end of the protected `Data`.
    ///
    /// - Parameter data: The `Data` to be appended.
    func append(_ data: Data) {
        write { (ward: inout T) in
            ward?.append(data)
        }
    }
}

// Dictionary 的线程安全方法
// 使用方式：定义变量时加上 @Protected ， 使用时带上$符号
// 例如：
// 定义 @Protected var atomicDict: [String: Int] = [:]
// 使用 self.$atomicDict["key"] = value
public extension Protected where T == Dictionary<AnyHashable, Any> {
    subscript(key: String) -> Any? {
        get {
            read { ward in
                return ward[key]
            }
        }
        set {
            write { (ward: inout T) in
                ward[key] = newValue
            }
        }
    }
}
